The trawler’s skipper spared no blushes in his assessment that the navy had been playing “Russian roulette” with the lives of his men.

Paul Murphy, who captains the trawler ‘Karen,’ said he was “furious” and told the BBC that if the navy cannot enter the Irish Sea with its boats “safely dived then they’ll have to come down on the surface.”

Investigators found that the report had been delayed by the military’s reluctance “to fully engage” with their work.

They found that the submarine’s crew had decided the trawler was a merchant vessel and that it was safe to pass beneath it.

Commanders decided that “the majority of shipping contacts in the area were merchant vessels” when in fact they were overwhelmingly trawlers.

Head investigator Steve Clinch told the BBC that “there is no reason” the submarine “should have been doing what she was.”

“The navy need to look at that and make sure that their commanders adhere to the code,” he added.

A Navy spokesperson said: “We have expressed our regret and remain sorry for the incident and delay in confirming our involvement.

“We’ve revised our procedures to reduce the risk that such an incident could happen again.”

The spokesman insisted the navy was “reviewing the report’s recommendations and continue to work closely with the maritime community to maximise safety.”